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United States Patent |
5,145,912
|
Hauenstein
,   et al.
|
September 8, 1992
|
Method for preparing oximosilane-functional vinylic copolymers
Abstract
An efficient method for preparing an oximosilane-functional vinylic
copolymer is disclosed wherein the corresponding alkoxysilane-functional
vinylic copolymer is reacted with an organoketoxime in a dry environment.
The oximosilane-functional vinylic copolymers produced by the method of
the present invention find utility in moisture-curable coating systems.
Inventors:
|
Hauenstein; Dale E. (Midland County, MI);
Vincent; Harold L. (Midland County, MI)
|
Assignee:
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Dow Corning Corporation (Midland, MI)
|
Appl. No.:
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628530 |
Filed:
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December 17, 1990 |
Current U.S. Class: |
525/326.5; 525/377 |
Intern'l Class: |
C08F 030/08 |
Field of Search: |
525/474,326.5,377
|
References Cited
U.S. Patent Documents
3453230 | Jul., 1969 | Plueddemann | 260/41.
|
4043953 | Aug., 1977 | Chang et al. | 260/18.
|
4157321 | Jun., 1979 | Kawakami et al. | 260/29.
|
4499150 | Feb., 1985 | Dowbenko et al. | 428/447.
|
4578417 | Mar., 1986 | Kurukawa et al. | 524/378.
|
4684697 | Aug., 1987 | Chang et al. | 525/100.
|
4714738 | Dec., 1987 | Chang et al. | 525/58.
|
4795783 | Jan., 1989 | Hunt | 525/101.
|
4925964 | May., 1990 | Zoche | 556/422.
|
Other References
Noll, Chem. and Tech. of Silicones, 1968 pp. 82 and 110.
|
Primary Examiner: Marquis; Melvyn I.
Assistant Examiner: Aylward; D. E.
Attorney, Agent or Firm: Weitz; Alexander
Claims
We claim:
1. A method for preparing an oximosilane-functional vinylic copolymer
comprising:
reacting an alkoxysilane-functional vinylic copolymer (I) with an
organoketoxime (II), said alkoxysilane-functional vinylic copolymer having
recurring units represented by the formula
##STR15##
wherein R is selected from the group consisting of hydrogen and alkyl
radicals having 1 to 3 carbon atoms, R.sup.1 is a divalent organic
radical, R.sup.2 is an alkyl radical having 1 to 6 carbon atoms, R.sup.3
is selected from the group consisting of alkyl radicals having 1 to 6
carbon atoms, a phenyl radical, a styryl radical and an alpha-methylstyryl
radical, x is an integer having a value of 1 to 3 and --Q-- represents a
residue of an ethylenically unsaturated organic monomer, said reaction
being carried out in a dry environment.
2. The method according to claim 1, wherein R.sup.1 of said
alkoxysilane-functional vinylic copolymer (I) is an ester selected from
the group consisting of those represented by the formulas
##STR16##
in which R.sup.4 is an alkylene group having 1 to 6 carbon atoms, R.sup.2
is an alkyl radical having 1 to 6 carbon atoms, R.sup.3 is selected from
the group consisting of alkyl radicals having 1 to 6 carbon atoms, and m
and n are each integers having a value of 1 to 6.
3. The method according to claim 2, wherein said organoketoxime (II) is
represented by the general formula
##STR17##
in which R.sup.5 and R.sup.6 are each selected from the group consisting
of alkyl radicals having 1 to 6 carbon atoms.
4. The method according to claim 3, wherein R.sup.2 of said
alkoxysilane-functional vinylic copolymer (I) is a methyl radical.
5. The method according to claim 4, wherein x of said
alkoxysilane-functional vinylic copolymer (I) is 3.
6. The method according to claim 5, wherein R.sup.1 is represented by the
formula
--C(O)O--CH.sub.2 CH.sub.2 CH.sub.2 --.
7. The method according to claim 1, wherein R.sup.1 of said
alkoxysilane-functional vinylic copolymer is an alkylene group having 1 to
6 carbon atoms.
8. The method according to claim 7, wherein said organoketoxime (II) is
represented by the general formula
##STR18##
in which R.sup.5 and R.sup.6 are each selected from the group consisting
of alkyl radicals having 1 to 6 carbon atoms.
9. The method according to claim 8, wherein R.sup.2 of said
alkoxysilane-functional vinylic copolymer (I) is a methyl radical.
10. The method according to claim 9, wherein x of said
alkoxysilane-functional vinylic copolymer (I) is 3.
11. The method according to claim 10, wherein R.sup.1 is a tetramethylene
group.
12. The method according to claim 1, wherein R.sup.1 of said
alkoxysilane-functional vinylic copolymer (I) is an amide group
represented by --C(O)N(H)R.sup.4 --, in which R.sup.4 is an alkylene group
having 1 to 6 carbon atoms.
13. The method according to claim 12, wherein said organoketoxime (II) is
represented by the general formula
##STR19##
in which R.sup.5 and R.sup.6 are each selected from the group consisting
of alkyl radicals having 1 to 6 carbon atoms.
14. The method according to claim 13, wherein R.sup.2 of said
alkoxysilane-functional vinylic copolymer (I) is a methyl radical.
15. The method according to claim 14, wherein x of said
alkoxysilane-functional vinylic copolymer (I) is 3.
16. The method according to claim 15, wherein R.sup.1 is represented by the
formula
--C(O)N(H)--CH.sub.2 CH.sub.2 CH.sub.2 CH.sub.2 CH.sub.2 CH.sub.2 --.
Description
FIELD OF THE INVENTION
The present invention relates to a method for preparing an
oximosilane-functional vinylic copolymers. More particularly, this
invention relates to a method for preparing these copolymers wherein an
alkoxysilane-functional vinylic copolymer is reacted with an
organoketoxime, this reaction being more effective than prior art addition
polymerization methods.
BACKGROUND OF THE INVENTION
There has been considerable recent interest in the development of new
ambient cure coating systems. A major consideration in this regard is the
desire to replace existing systems which require elevated cure
temperatures, systems which contain or release toxic substances during
cure, and systems which are generally slow to cure.
For example, in the "color-plus-clear" coating systems for automotive
topcoats, final coats of a clear coating are applied over a pigmented
basecoat. Known color-plus-clear coating systems based on thermosetting
resins require cure temperatures of at least 120.degree. C. In addition,
one- and two-part polyurethane systems rely on organic isocyanates for
their cure, and therefore suffer from the physiological hazards associated
with the inhalation of, or skin contact with, these compounds. In an
effort to overcome these disadvantages, current technology has focused on
the use of systems which rely on alkoxysilane functionality for a less
toxic, more rapid ambient cure mechanism.
U.S. Pat. No. 4,499,150 to Dowbenko et al. discloses a color-plus-clear
coating method wherein a vinylic addition copolymer containing
alkoxysilane and/or acyloxysilane functionality is present in either the
basecoat or the topcoat. However, the curing time of such a system may
still be slow, even when a curing catalyst, such as dibutyltin dilaurate,
dibutyltin dimaleate or tetrabutyl titanate is added. A prolonged cure
time after application of the coating to the substrate can result in
cracks or other undesirable properties.
The above application of a vinylic copolymer which contains hydrolyzable
silane moieties in its molecule is but one illustration of the utility of
such systems. Of these copolymers, those having oximosilane-functional
groups can offer particular advantages as ambient cure, one-part coatings:
they exhibit faster, more thorough cure and they show improved physical
and chemical properties over the corresponding alkoxysilane-functional
copolymer coatings.
However, as desirable as these oximosilane-functional vinylic copolymers
may be, their heretofore disclosed methods of preparation are somewhat
limited and have been observed to be relatively inefficient relative to
our discovered preparative method, described infra. Thus, to date,
essentially three procedures have been describe for the preparation of
vinylic copolymers containing various types of hydrolyzable silane
functionality. For example, Plueddemann, in U.S. Pat. No. 3,453,230,
teaches room temperature curable acrylate rubbers wherein a mixture of an
acrylic monomer, a silane monomer which contains an unsaturated group as
well as a hydrolyzable group, a mercapto-functional silane and a free
radical catalyst is polymerized in the absence of water. The resulting
copolymer can be cured by exposure to moist air.
In U.S. Pat. No. 4,157,321 to Kawakami et al., copolymers of an
ethylenically unsaturated organic monomer and an unsaturated organosilane
monomer are shown to be stabilized by the addition of a compound selected
from monomeric hydrolytically reactive organosilanes or trialkyl
orthoformates. The copolymers of this invention are prepared by
conventional addition polymerization methods.
Furukawa et al., in U.S. Pat. No. 4,578,417, disclose a moisture curable
composition having improved storage stability comprising a hydrolyzable
silyl group-containing vinyl polymer and an orthoacetic acid ester as a
stabilizer. The polymers of this contribution to the art are said to be
prepared by either the above mentioned addition polymerization technique
or by hydrosilation of a vinyl polymer having a carbon-carbon double bond
with a hydrosilane.
U.S. Pat. No. 4,795,783 to Hunt teaches coating compositions which comprise
a blend of a hydroxyl-functional vinyl polymer and an organopolysiloxane
containing hydrolyzable groups. The latter, in turn, is prepared by the
partial hydrolysis of a silane containing hydrolyzable groups.
Chang et al. teach acrylic-silane copolymer compositions in U.S. Pat. Nos.
4,043,953, 4,684,697 and 4,714,738. Again, these disclosures do not
suggest the method of the present invention, but do discuss three
conventional ways to prepare the copolymers. One of these methods is the
above mentioned procedure of addition polymerization of an acrylic monomer
together with an alkoxysilane having acrylic functionality thereon in the
presence of a free radial initiator. A second method involves the
hydrosilation of an acrylic addition copolymer containing carbon-carbon
double bonds with a hydrosilane in the presence of a transition metal
catalyst. The third method contemplates a reaction between a
hydroxyl-functional acrylic resin with a minimal quantity of certain
organosilicon-containing materials, such as organosilicates or their
partial hydrolysis products.
SUMMARY OF THE INVENTION
Although the above discussed methods for the preparation of vinylic
copolymers containing various hydrolyzable silane groups do yield the
desired products, inventors have discovered an alternate method for
producing oximosilane-functional vinylic copolymers which is highly
efficient. Thus, for example, the most common and straightforward
conventional method for preparing these vinylic copolymers is the addition
copolymerization of organic vinylic monomers with the appropriate
silane-functional vinylic monomer in the presence of a free radical
initiator, as briefly described supra. Applicants have found, however,
that such a procedure is relatively inefficient when an
oximosilane-functional vinylic monomer is one of the reactants of the
addition polymerization scheme. While not wishing to be bound by any
theoretical consideration or a particular mechanistic interpretation, it
is believed that the oximosilane functionality may partially deactivate
the free radical initiator required to effect the addition polymerization.
This drawback is overcome by the present method since no free radical
initiator is required during the reaction of the alkoxysilane-functional
vinylic copolymer (which can be efficiently produced by a routine addition
polymerization procedure) with the organoketoxime.
The present invention therefore relates to a method for preparing an
oximosilane-functional vinylic copolymer comprising reacting an
alkoxysilane-functional vinylic copolymer (I) with an organoketoxime (II),
said alkoxysilane-functional vinylic copolymer having recurring units
represented by the formula
##STR1##
wherein R is selected from the group consisting of hydrogen and an alkyl
radical having 1 to 3 carbon atoms, R.sup.1 is a divalent organic radical,
R.sup.2 is an alkyl radical having 1 to 6 carbon atoms, R.sup.3 is
selected from the group consisting of alkyl radicals having 1 to 6 carbon
atoms, a phenyl radical, a styryl radical and an alpha-methylstyryl
radical, x is an integer having a value of 1 to 3 and --Q-- represents a
residue of an ethylenically unsaturated organic monomer, said reaction
being carried out in a dry environment.
DETAILED DESCRIPTION OF THE INVENTION
The method of the present invention involves the reaction of an
alkoxysilane-functional vinylic copolymer (I) with an organoketoxime (II)
to produce an oximosilane-functional vinylic copolymer.
The alkoxysilane-functional vinylic copolymer of this invention has
recurring units represented by the formula
##STR2##
wherein R is selected from the group consisting of hydrogen and an alkyl
radical having 1 to 3 carbon atoms. In formula (I), R.sup.1 is a divalent
organic radical containing carbon, hydrogen and, optionally, oxygen and/or
nitrogen atoms. It is preferred that R.sup.1 is selected from an alkylene
group having from 1 to 6 carbon atoms, an amide group having the formula
--C(O)N(H)R.sup.4 --, or an ester group having the formula
##STR3##
or --C(O)OR.sup.4 --, in which R.sup.4 is an alkylene group having 1 to 6
carbon atoms and the values of the integers m and n can be 1 to 6. The
group R.sup.2 in the preceding formulas is an alkyl radical having 1 to 6
carbon atoms, R.sup.3 in the preceding formulas is selected from the group
consisting of alkyl radicals having 1 to 6 carbon atoms, a phenyl radical,
a styryl radical and an alpha-methylstyryl radical and x is an integer
having a value of 1 to 3. The divalent group Q in formula (I) represents
the residue of an ethylenically unsaturated, silicon-free organic monomer,
described infra.
As is well documented in the art, the above mentioned
alkoxysilane-functional vinylic copolymer (I) may readily be prepared by
the free radical addition copolymerization of at least one ethylenically
unsaturated organic monomer, which forms the residue Q of formula (I),
with an alkoxysilane-functional ethylenically unsaturated monomer having
the following general formula, wherein R, R.sup.1, R.sup.2, R.sup.3 and x
have their above defined meanings.
##STR4##
In brief, the copolymerization procedure generally involves the slow
introduction of a mixture of the appropriate monomers into a preheated
organic solvent system. A free radical initiator, such as a peroxide,
peroxyester or nitrile type, is added either to the initial solvent system
or to the monomer mix before the addition is started. The reaction is
carried out in an inert atmosphere since the free radical initiator is
generally deactivated by oxygen.
The above mentioned ethylenically unsaturated organic monomers which form
the residue Q of formula (I) may be selected from compounds recited in,
e.g., above mentioned U.S. Pat. No. 4,157,321 to Kawakami et al. Among
others, these include alkyl acrylates, such as methyl acrylate, ethyl
acrylate, propyl acrylate, butyl acrylate, hexyl acrylate, octyl acrylate,
methyl methacrylate, butyl methacrylate lauryl methacrylate, isobornyl
methacrylate, lauryl acrylate, isobornyl acrylate, and octyl methacrylate;
vinyl aromatic hydrocarbons, such as styrene, vinyl toluene and
alpha-methyl styrene; vinyl and vinylidene halides, such as vinyl chloride
and vinylidene chloride; conjugated dienes, such as butadiene and
isoprene; and vinyl esters, such as vinyl acetate and vinyl propionate.
In addition to the above described organic monomers which form the residue
Q of formula (I), the following fluorinated structures may be used:
##STR5##
in which R has its previously defined meaning and R.sup.F is a
perfluorinated alkyl radical having 3 to 8 carbon atoms. Examples of such
fluorinated organic monomers include structures such as
##STR6##
In applying the method of the present invention, it is preferred that the
ethylenically unsaturated organic monomers are selected from acrylate and
methacrylate structures, most preferably, methyl methacrylate, butyl
methacrylate, ethyl methacrylate, isobutyl methacrylate, methyl acrylate,
butyl acrylate, ethyl acrylate, and isobutyl acrylate. It is likewise
preferred that the above mentioned alkoxysilane-functional vinylic monomer
of formula (Ia) is selected from an acrylamide type, wherein R.sup.1 has
the structure --C(O)N(H)R.sup.4 --, an alkenyl type, wherein R.sup.1 is an
alkylene group having 1 to 6 carbon atoms or an acrylic type, wherein
R.sup.1 has the structure --C(O)OR.sup.4 --, R.sup.4 of the previous
formulas having its previously defined meaning. An acrylic type of
alkoxysilane-functional monomer is highly preferred wherein R.sup.1 of
formula (Ia) is --C(O)OR.sup.4 --, in which R.sup.4 is an alkylene group
having 1 to 6 carbon atoms, R of formula (Ia) is hydrogen or a methyl
radical and R.sup.2 of formula (Ia) is a methyl radical.
Examples of highly preferred alkoxysilane-functional monomers which may be
copolymerized with the above mentioned preferred ethylenically unsaturated
organic monomers, are represented by the following formulas. Formula (Ib)
illustrates an acrylic type of alkoxysilane-functional monomer.
##STR7##
wherein Me hereinafter denotes a methyl radical and R is either H or Me.
Formula (Ic) illustrates an acrylamide type of alkoxysilane-functional
monomer.
##STR8##
wherein R is either H or Me.
Formulas (Id) and (Ie) illustrate alkenyl types of alkoxysilane-functional
monomers.
##STR9##
wherein Et hereinafter denotes an ethyl radical.
The organoketoxime (II) which is reacted with the above described
alkoxysilane-functional vinylic copolymer (I) may be any organic compound
having the general functionality
##STR10##
in its structure. The only limitation on the organic groups of the above
structure is that they be inert and not react with component (I) or
otherwise detract from carrying out the method described herein.
Preferably, these compounds are diorganoketoximes, such as those
represented by the general formula
##STR11##
in which R.sup.5 and R.sup.6 are each selected from the group consisting
of alkyl radicals having 1 to 6 carbon atoms.
Alternatively, component (II) can have a structure such as
##STR12##
wherein R.sup.7 is a cyclic divalent hydrocarbon species, such as a
cyclohexyl type radical (i.e., --C.sub.6 H.sub.10 --), and R.sup.5 has its
previously defined meaning.
The above organoketoxime compounds are well known in the art and some are
available commercially. They may be prepared by reacting the corresponding
ketone with hydroxylamine. Specific examples of this component include
dimethylketoxime, methylethylketoxime, methylbutylketoxime,
methylpropylketoxime, diethylketoxime, benzylmethylketoxime and
methylphenylketoxime.
For the purposes of the present invention, it is preferred that
organoketoxime (II) is methylethylketoxime, which has the structure
##STR13##
In order to practice the method of the present invention, the
alkoxysilane-functional vinylic copolymer (I) and the organoketoxime (II)
are reacted with each other by simply mixing these components at elevated
temperatures, such as 55.degree. to 80.degree. C., for example. It is
preferred that the temperature is sufficient to boil off the byproduct
alcohol formed in the reaction of the alkoxy groups of component (I) with
the ketoxime functionality of component (II). The following reaction
illustrates this process for the case of a trimethoxysilane-functional
compound reacting with methylethylketoxime to form the corresponding
oximosilane-functional compound and methanol as a byproduct.
##STR14##
In the above case, the reaction can be effectively completed within about
300 minutes at or near the boiling point of the methanol (i.e.,
approximately 65.degree. C.). It is also possible to use lower
temperatures if a vacuum is applied during the reaction to remove the
byproduct alcohol.
It is further preferred that the reaction be carried out in an inert
organic solvent, such as toluene, xylene, mineral spirits, VM & P naphtha
or methylisobutyl ketone. These solvents are typically present during the
formation of the alkoxysilane-functional vinylic copolymer (I) and may be
retained during the above described reaction. Alternatively, the reaction
can be run at 100 percent solids, but this is less preferred since
viscosity is greater and reactivity is diminished. When a solvent is
employed, components (I) and (II) should comprise from about 15 to about
65 weight percent of the total reaction mixture.
The skilled artisan will, of course, appreciate the need for conducting the
above reaction in the absence of moisture since both the alkoxysilane and
the oximosilane functionalities are susceptible to hydrolysis. Thus, it is
preferred to react the components in a dry inert gas atmosphere in order
to preserve the integrity of the hydrolyzable groups. However, it should
be noted that unlike the case of the aforementioned addition
polymerization reactions, there is no particular need to exclude oxygen
from the reaction vessel as there is no concern for the deactivation of a
free radical initiator in this instance.
The proportions of components (I) and (II) to be used in the instant method
are preferably such that about 0.5 to about 1.5 equivalents of the
organoketoxime is used for each equivalent of alkoxy functionality present
in the alkoxysilane-functional vinylic copolymer. Preferably, an excess of
the organoketoxime is employed wherein 1.5 equivalents of the
organoketoxime is used for each equivalent of alkoxy functionality.
After the oximosilane-functional vinylic copolymers of the present
invention are prepared, it is preferred that a stabilizing amount of an
oximosilane crosslinker is added in order to prevent viscosity drift
and/or gellation. Typical oximosilanes which may be used for this purpose
include such compounds as taught in U.S. Pat. No. 3,189,576 to Sweet:
(MeEtC=NO).sub.3 SiVi (vinyltris(methylethylketoximine)silane),
(MeEtC=NO).sub.3 SiMe (methyltris(methylethylketoximine)silane) and
(MeEtC=NO).sub.4 Si (tetrakis(methylethylketoximine)silane), in which Vi
denotes a vinyl radical.
The oximosilane-functional vinylic copolymers produced by the method of the
present invention find utility as moisture-curable coating systems. They
are particularly suitable in replacing systems which require elevated
temperatures for cure, systems which contain or release toxic components
during their cure and systems which are generally slow to cure.
EXAMPLES
The following examples are presented to further illustrate the method of
this invention, but are not to be construed as limiting the invention,
which is delineated in the appended claims. All parts and percentages in
the examples are on a weight basis and all measurements were obtained at
25.degree. C., unless indicated to the contrary.
EXAMPLE 1
This example illustrates the preparation of an oximosilane-functional
acrylic monomer.
Into a 1000-ml glass 3-neck round-bottom flask, equipped with a condenser
fitted with a Dean-Stark trap, a stirrer, a nitrogen inlet, a thermometer
and a temperature regulator, there was charged 150 grams of
3-methacryloxypropyltrimethoxysilane, 235 grams of methylethylketoxime
(Mooney Chemical, Inc., Cleveland, OH) 115 grams of dry toluene, and 2
grams of magnesium oxide (Magnox.TM. 98 HR Fine; Basic Incorporated,
Valley Forge, PA). Three drops of diethyl hydroxylamine was added as a
polymerization inhibitor. The mixture was slowly heated to 130.degree. C.
while stirring under a nitrogen atmosphere. Methanol byproduct of the
reaction was collected in the Dean-Stark trap. Excess reactants were
stripped off under a vacuum down to 31 mm Hg as the temperature slowly
rose to 135.degree. C. The product of the reaction was then cooled to
below 40.degree. C., filtered and packaged under a nitrogen blanket.
Infrared analysis showed an 85-90% conversion of methoxy groups to oxime
groups.
EXAMPLE 2
This example illustrates the preparation of an intermediate copolymer of
the present invention by a conventional addition polymerization method
wherein an alkoxysilane-functional acrylic monomer and a combination of
acrylate monomers was reacted in the presence of a free radical initiator.
Into a 1000-ml glass 3-neck round-bottom flask equipped with a thermometer,
condenser, stirrer, heating mantle, temperature control, addition funnel
and nitrogen inlet, there was added 150.34 grams of toluene
(Fisher-Certified grade) which had previously been dried over molecular
sieves. The toluene was heated to 98.degree. C. under the nitrogen
blanket. A mixture of 57.66 grams of toluene, 30.00 grams of
3-methacryloxypropyltrimethoxysilane, 110.00 grams methyl methacrylate
(Rohm and Haas, Philadelphia, PA) containing 10 ppm of methylhydroquinone
(MEHQ), 20.00 grams of butyl methacrylate containing 10 ppm of MEHQ (Rohm
and Haas), 40.00 grams of styrene (Fisher Certified grade; 50 ppm of
t-butylcatechol) and 8.00 grams of t-butylperoxyacetate, marketed under
the trade name Lupersol.TM. 70 (Pennwalt Corp., Buffalo, NY), was placed
in the addition funnel.
The above monomer mixture was added slowly (approximately 140 drops per
minute) to the flask over a period of 3 hours. The temperature was held at
103.degree.-105.degree. C. for 1 hour after the addition of the monomers.
The resulting solution was allowed to cool below 45.degree. C. and
packaged under nitrogen. Essentially complete conversion of the monomers
to a copolymer was evidenced by the observation that the final solids
content was 48.4% versus a theoretical solids content of 49.0% based upon
the initial charge.
(COMPARATIVE) EXAMPLE 3
This example illustrates a conventional addition polymerization of an
oximosilane-functional monomer with a combination of acrylate monomers to
prepare an oximosilane-functional acrylic copolymer.
The procedure of Example 2 was followed wherein 150.08 grams of toluene was
heated in a flask to 92.degree. C. A mixture of 29.00 grams of toluene,
15.01 grams of the oximosilane-functional acrylic monomer produced in
Example 1, 55.01 grams of methyl methacrylate, 10.01 grams of butyl
methacrylate, 20.00 gram styrene and 4.02 grams of t-butylperoxyacetate
was charged to the addition funnel.
The above monomer mix was slowly added (approximately 100 drops per minute)
to the flask over a period of 1 hour. The temperature was held between
97.degree.-100.degree. C. for 1 hour after the addition of the monomers.
The resulting solution was allowed to cool below 45.degree. C. and
packaged under nitrogen.
A relatively incomplete reaction was indicated since the copolymer solution
had a solids content of 17% versus a theoretical solids content of 35.8%
based on the initial monomer charge.
(COMPARATIVE) EXAMPLE 4
In this example, the conventional addition copolymerization of an
oximosilane-functional monomer with a combination of acrylate monomers was
repeated to show the effect of excess initiator.
Toluene (125.06 grams) was heated in a flask to 94.degree. C. A mixture of
25.04 grams of toluene, 15.07 grams of the oximosilane-functional acrylic
monomer produced in Example 1, 10.00 grams of methyl methacrylate, 55.07
grams of butyl methacrylate, 24.02 gram of styrene and 4.04 grams of
t-butylperoxyacetate was charged to the addition funnel.
The above monomer mix was slowly added (approximately 140 drops per minute)
to the flask containing over a period of 45 minutes. The temperature was
held between 100.degree.-104.degree. C. for 1 hour after the addition of
the monomers. The resulting solution was cooled to approximately
40.degree. C. and packaged under nitrogen.
As in (Comparative) Example 3, the low copolymer solids content (21.1%
versus a theoretical value of 41.0% based on the initial charge) confirmed
the inefficient nature of this reaction procedure.
The above copolymer solution was reheated to 95.degree. C. and a solution
of 1 gram of t-butylperoxyacetate in 23.00 gram toluene was placed in the
addition funnel and added to the copolymer solution at a rate of
approximately 109 drops/minute over a period of 27 minutes. The
temperature was held between 96.degree.-100.degree. C. for 1 hour after
the addition of the t-butylperoxyacetate solution.
The above copolymer solution was then cooled to approximately 40.degree. C.
and packaged under nitrogen. The solids content of this solution was now
28.6%, indicating that the addition of extra initiator
(t-butylperoxyacetate) resulted in only a modest increase in copolymer
yield.
EXAMPLE 5
This example illustrates the preparation of an oximosilane-functional
acrylic copolymer by the method of the present invention wherein
methylethylketoxime was reacted with an alkoxysilane-functional acrylic
copolymer.
To a 500-ml glass round-bottom flask, equipped as described in Example 1,
there was added 100.0 grams of the alkoxysilane-functional acrylic
copolymer solution produced in Example 2, and 12.0 grams of
methylethylketoxime. This combination was stirred under a nitrogen
blanket, slowly heated to 75.degree. C. and then maintained at
71.degree.-78.degree. C. for 5 hours. Methanol formed during the reaction
was collected in the Dean-Stark trap. The contents were allowed to cool to
below 45.degree. C. and then packaged under nitrogen.
The efficiency of this reaction was evidenced by the relatively high solids
content observed (42.6%) versus a theoretical solids content of 42.3%.
This result, in combination with the high efficiency of the reaction
described in Example 2, exemplifies the advantage of the method of the
present invention in the preparation of an oximosilane-functional acrylic
copolymer.
EXAMPLE 6
This example illustrates another preparation of an intermediate copolymer
by a conventional addition polymerization method wherein an
alkoxysilane-functional acrylic monomer and a combination of acrylic
monomers was reacted in the presence of a free radical initiator.
A similar procedure to that described in Example 2 was followed wherein
350.0 grams of xylene (Fisher-Certified grade) which had previously been
dried over molecular sieves was heated to 100.degree. C. under the
nitrogen blanket. A mixture of 50.0 grams of xylene, 70.3 grams of
3-methacryloxypropyltrimethoxysilane, 141.8 grams methyl methacrylate,
203.6 grams of butyl methacrylate and 16.4 grams of t-butylperoxyacetate
was placed in the addition funnel.
The above monomer mixture was added slowly (approximately 205 drops per
minute) to the flask over a period of 80 minutes. The temperature was held
at 100.degree.-102.degree. C. for 1.5 hours after the addition of the
monomers. The resulting solution was allowed to cool below 47.degree. C.
and packaged under nitrogen.
This procedure resulted in a copolymer solution having a solids content of
51% (versus a theoretical solids content of 51% based on the initial
charge).
EXAMPLE 7
This example illustrates another preparation of an oximosilane-functional
acrylic copolymer according to the methods of the present invention.
To a 500-ml glass round-bottom flask, equipped as described in Example 1,
there was added 101.6 grams of the alkoxysilane-functional acrylate
copolymer solution produced in Example 6, 21.0 grams of dried xylene and
13.0 grams of methylethylketoxime. This combination was stirred under a
nitrogen blanket, slowly heated to 79.degree. C. and then maintained at
77.degree.-82.degree. C. for about 2.5 hours. Methanol formed during the
reaction was collected in the Dean-Stark trap. The contents were allowed
to cool to below 45.degree. C. and then packaged under nitrogen.
The efficiency of this reaction was evidenced by the relatively high solids
content observed (39.1%) versus the theoretical solids content (39.6%).
EXAMPLE 8
This example illustrates a method of stabilizing the oximosilane-functional
acrylic polymers produced according to the method of the present
invention.
Various quantities of an oxime crosslinker, consisting essentially of
methyltris(methylethylketoximine)silane and
methyldi(methylethylketoximine)methoxysilane in a ratio of about 2.6:1,
respectively, were mixed with the oximosilane-functional acrylic copolymer
solution of Example 7, as shown in Table 1. These mixtures were used to
fill 1-ounce vials so as to provide a headspace of about 3/4 to 4/5 of the
vial volume. The vials were observed for a period of 65 days and the
consistency of the mixtures noted as a function of storage time at
22.degree.-25.degree. C. The time of gelation (i.e., when the mixture
would not flow) was noted and is reported in Table 1.
TABLE 1
______________________________________
WT % COPOLYMER
WT % OXIME GELATION
(EXAMPLE 7) CROSSLINKER TIME (DAYS)
______________________________________
100.0 0.0 0.67
99.5 0.5 19
99.0 1.0 26
97.0 3.0 48
95.0 5.0 *(skin-over at 65
days)
90.0 10.0 *
85.0 15.0 *
80.0 20.0 *
70.0 30.0 *
50.0 50.0 *
______________________________________
*Flowable for more than 65 days.
It is seen that relatively stable oximosilane-functional acrylic copolymer
can be obtained when at least about 5% of the above mentioned oxime
crosslinker is added thereto.
For comparative purposes, the alkoxysilane-functional acrylic copolymer of
Example 6 was similarly modified with tetrabutyl titanate (TBT) and
methyltrimethoxysilane (MTMS), according to a conventional method
practiced in the art for this type of copolymer. Table 2 shows the
relative proportions of these ingredients in addition to the gel time
observations described above.
TABLE 2
______________________________________
WT %
COPOLYMER GELATION
(EXAMPLE 6)
WT % TBT WT % MTMS TIME (DAYS)
______________________________________
100.0 -- -- 27
99.5 0.5 -- 1
99.5 -- 0.5 27
99.3 0.5 0.2 1
99.0 0.5 0.5 1
98.5 0.5 1.0 2
97.6 0.5 2.0 7
96.5 0.5 3.0 27
95.5 0.5 4.0 27
94.5 0.5 5.0 56
92.0 0.5 7.5 *
89.5 0.5 10.0 *
79.5 0.5 20.0 *
69.5 0.5 30.0 *
49.5 0.5 50.0 *
______________________________________
*Flowable for more than 65 days.
Comparison of Tables 1 and 2 suggests that the oximosilane-functional
acrylic copolymers of the present invention can be readily stabilized to
approximately the same degree as conventional alkoxysilane-functional
acrylic copolymers.
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